# SIG_ERR

From cppreference.com
< c‎ | program

Defined in header ``<signal.h>`` |  |
#define SIG_ERR /* implementation defined */ |  |

A value of type `void (*)(int)`. When returned by signal, indicates that an error has occurred.

### Example

Run this code

    #include <stdio.h>
    #include <stdlib.h>
    #include <signal.h>

    void signal_handler(int sig)
    {
        printf("Received signal: %d\n", sig);
    }

    int main(void)
    {
        /* Install a signal handler. */
        if (signal(SIGTERM, signal_handler) == SIG_ERR)
        {
            printf("Error while installing a signal handler.\n");
            exit(EXIT_FAILURE);
        }

        printf("Sending signal: %d\n", SIGTERM);
        if (raise(SIGTERM) != 0)
        {
            printf("Error while raising the SIGTERM signal.\n");
            exit(EXIT_FAILURE);
        }

        printf("Exit main()\n");
        return EXIT_SUCCESS;
    }

Output:

    Sending signal: 15
    Received signal: 15
    Exit main()

### References

- C17 standard (ISO/IEC 9899:2018):

  - 7.14/3 Signal handling <signal.h> (p: 194)

- C11 standard (ISO/IEC 9899:2011):

  - 7.14/3 Signal handling <signal.h> (p: 265)

- C99 standard (ISO/IEC 9899:1999):

  - 7.14/3 Signal handling <signal.h> (p: 246)

- C89/C90 standard (ISO/IEC 9899:1990):

  - 4.7 SIGNAL HANDLING <signal.h>

### See also

signal | sets a signal handler for particular signal (function)
C++ documentation for SIG_ERR

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